1. Field of the Invention
The present invention relates to an electronic protection device for protecting at least one electrical component connectable to the protection device. The invention relates further to a method for operating an electronic protection device and the use of an electronic protection.
2. Description of the Background Art
A number of protection devices whose purpose is to protect a voltage source and/or a load, connected to the voltage source, particularly from excessive currents are known from the state of the art.
Such protection devices were developed and employed even at the beginning of the industrial use of electrical energy, as, for example, U.S. Pat. No. 438,305 of T. A. Edison for a “fuse block” shows, which dates from a patent application from the year 1885. Such a fuse block, like the majority of safety fuses used today, has the disadvantage that after a fault event, therefore after the melting of the so-called fuse element, the existing safety fuse must be replaced by a new safety fuse.
To avoid having to replace a blown fuse after a fault event, for example, “self-resetting fuse elements,” which are also called “self-resetting thermal fuses,” were developed in the past. A number of versions of self-resetting fuse elements are commonly used. Among experts, self-resetting fuse elements are generally differentiated by the material used for their manufacture. Especially common self-resetting fuses are so-called “PTC fuses,” particularly PTC fuses with a polymer base, whereby these last-named fuses are often called a “PPTC fuse” (polymeric positive temperature coefficient fuse). Examples of self-resetting thermal fuse elements are described in the short form catalog “BOURNS® Multifuse®, Resettable Fuses—Polymer PTC & Ceramic PTC” from the year 2008.
In a further section of the description, reference will again be made to this short form catalog, designated as document “PD1” below.
In the following text, the term “self-resetting thermal fuse element” will be called a “fuse element” in short.
A disadvantage of a fuse element of the indicated type is that during its use a possible overloading of an electrical circuit can in fact be prevented for a calculable time period, but during relatively frequent or continuous operation of a fuse element in the “tripped state”, therefore in the substantially current-blocking state, due to a “continuous load” on the fuse element irreversible changes occur in the fuse element, which considerably shorten its lifetime. In other words, for example, the described continuous load on the fuse element leads to its premature aging, which depending on the occurrence of other boundary conditions can lead to the destruction of the fuse element, for example, under unfavorable boundary conditions even after a few days.
As a rule, the lifetime of a fuse element is the shorter, the longer (with regard to time) the fuse element is exposed to the aforementioned continuous load and the higher the temperature of the fuse element during the continuous load.
In cases in which, for example, a wiring error remains undetected for a longer period of time, for example, for a time interval of a number of days, weeks, or months, this can have serious consequences, for example, when the component connected to the fuse element is connected to a voltage source or a reference potential in such a way that the fuse element in the aforementioned time interval (days, weeks, or months) is kept substantially continuously in the “tripped,” therefore blocking state. The destruction of the fuse element, possibly occurring after this type of continuous load, can subsequently bring about a considerably increased current through the fuse element, which can lead to the destruction of a connected electrical component, originally protected by the fuse element, or other components.
Other resultant problems of a destroyed fuse element, which no longer performs the intended function, under certain boundary conditions can even be that the fuse element burns away, which ultimately can lead to the destruction of entire component groups of an electrotechnical device and other adjacent items, which are in physical proximity to the burning fuse element.
Furthermore, an often insufficiently high or an insufficiently low tripping delay is disadvantageous in the case of protection devices, which only use a fuse element for protection from an overcurrent. In fact, the user or developer of a protection device, which only has a fuse element, can influence the tripping delay of the protection device to a limited extent, in that the employed fuse element is selected from the standpoint of circuit tripping delay, but ultimately there continues to be an enormous dependence on the design specifications of the fuse element manufacturer. The protection device parameters present after the fuse element manufacturing process are determined by these design specifications.
In other words, the user or developer does not have a simple, practically usable method to change the time switching behavior selectively and predictably. In cases in which the protection devices consist only of fuse elements, in regard to the tripping delay of the protection device, developers or users are therefore committed to the respective parameters of the fuse element manufacturer.
A further disadvantage of a protection device according to the state of the art, which consists, for example, solely of a fuse element, is the relatively great ability of the ambient temperature of the protection device to influence the parameters and hence the fault current response of the fuse element (called, for example, the “PTC response characteristic”).
Another example of prior-art protection devices is an electronic fuse. The publication of the international patent application WO 86/06223 A1, which corresponds to U.S. Pat. No. 4,752,852, can be cited for this purpose. According to this publication, a switch could be controlled by electrical pulses. As soon as the current exceeds a predetermined value, the electronic fuse could restrict the current flow by means of the switch. The time period during which the switch is closed by means of the pulse could shorten if the current increases due to a load. The switch could be opened completely when a predetermined maximum allowable current value is exceeded.